freq counter?

[Magnus Danielson]

From: Dave Halliday <daveh at microsoft.com>
Subject: RE: freq counter?
Date: Wed, 21 Jun 2000 11:20:18 -0700

> Another way to go for low ( audio range ) frequencies is to measure the
> period between waveforms.  This can be a royal bear with an irregular
> waveform but for simple sine/square waves, it can give really good accuracy.
> This doesn't give a direct frequency readout, it is 1/f but this can be
> calculated fairly easily.
> 
> 
> 
> Another way is to use an o-scope and a precision frequency source - use the
> scope in an XY mode and plug the known freq into one axis and the unknown
> but variable freq into the other.  When you get close to a straight line,
> the two are equal.

This is a way to measure their relative phase. The method you describe
is good for sine-like waveforms. A good scope method is to run the
waveforms alongside, use delayed trigger and zoom into the area, it's
a fairly simple method that allows good viewing of small phase
frequency deviations in graphical form. I have had people understand
their trouble only after such a session. Their jitter behavior became
quite apparent.

Cheers,
Magnus